Hi I'm new to Bonsai and gardening in general

Not a good combination. You need to go to the library & read up on basic plant
growth.

My Chinese elm has started dropping its leaves, they turn yellowish in
colour first
then drop off.

I take it you are either in Canada or UK. Try to find the nearest bonsai club.
Local people will be the most help.
Your tree is probably responding to being in the wrong place all winter. Put it
outdoors, starting in full shade, but do not allow it to go below freezing.
Very gradually get it into the sun. Do not overwater. Don't water it until the
soil starts to dry out. Next fall leave it outdoors until it goes dormant &
keep it in a cold location all winter. It should not have any leaves at this
time of year (or just starting to bud).

Iris,
Central NY, Zone 5a, Sunset Zone 40
"If we see light at the end of the tunnel, It's the light of the oncoming
train."
Robert Lowell (1917-1977)

In message , Iris Cohen
writes
Very gradually get it into the sun. Do not overwater. Don't water it until the
soil starts to dry out. Next fall leave it outdoors until it goes dormant &
keep it in a cold location all winter. It should not have any leaves at this
time of year (or just starting to bud).

I've put my photo up on the photo site (can't spell that word yet). As
you'll see mine didn't lose its leaves at all, yet its been outside ever
since I got it this time last year. Could (I'm told to quote zone8/8a
and you'll understand) my zone be too warm for the Zelkovas? We don't
see a lot of very hard frosts and the amount of snow I get would make an
eskimo laugh.

Sincerely, Chris
--
Chris McMillan
reply to:
http://homepage.ntlworld.com/mike.mcmillan/